How to Replace Fox Mustang In-Tank Fuel Pumps

Be it a failed pump or upgrading for performance, there are a few tricks to a successful replacement

January 14, 2014

Fuel injection systems utilize high-pressure fuel pumps that run between 40-60 psi (depending upon the application). These high-pressure pumps were frame-rail-mounted in the pioneering days of factory EFI, including some of the first fuel injected Fox Mustangs. However, as manufacturers learned about EFI and implemented changes to their model lineup, the high-pressure EFI fuel pump eventually made its way to the inside of the fuel tank. This in-tank mounting had several benefits, including packaging, noise reduction, and fuel pump life (the fuel itself is a cooling medium). Unfortunately, placing the fuel pump inside the fuel tank does make a fuel pump replacement or upgrade a little more challenging than removing a couple of bolts and swapping out pumps. In some vehicles, you can actually access the fuel pump through a large body plug directly over the tank (Ford started doing this with the '05 and up Mustang), but for the Fox-era Mustang it requires removal of the fuel tank from the vehicle to access the fuel pump assembly. This is still very much a DIY project that can be accomplished with basic hand tools in your driveway. You just have to remember you are dealing with a flammable material and to ensure you are using safe procedures. Replacement fuel pumps are available in stock flow and high-flow models. If your Mustang is completely stock, then a stock pump is fine. However, if you have performance upgrades or are planning said upgrades, a higher flow fuel pump should be on your shopping list. There are a few other “gotchas” we'll discuss in the captions, but this is indeed a project you can tackle easily. See how in the photos with the help of National Parts Depot's Fox Mustang catalog.